Flame retardant masterbatch composition for foams containing a ph moderator

ABSTRACT

A masterbatch composition suitable for use as a flame retardant in extruded polymer foams, and process for manufacturing the same, and extruded foams containing same; the composition comprising: (a) 20 to 40 parts by weight base resin comprising styrene homopolymer or copolymer; (b) 1 to 16 parts by weight acid scavenger comprising an epoxy-based compound; (c) 2 to 6 parts by weight antioxidant comprising an alkyl or aryl phosphite; and (d) 45 to 60 parts by weight flame retardant comprising a non-hexabromocyclododecane (HBCD) brominated polymer or copolymer, wherein the amounts of (a), (b), (c), and (d) total 100 parts by weight; and (e) 0.6 to 10 parts by weight of pH moderator, based on 100 parts of (a) base resin plus (e) water soluble pH moderator.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to stabilized environmentally-friendlymasterbatch compositions that contain a brominated polymeric flameretardant, specifically masterbatch compositions that are suitable foruse in solid foams as an additive composition.

Description of Related Art

Various environmentally-friendly brominated organic-based polymericflame retardants (FR) compounds, such as those disclosed in Kram, etal., U.S. Pat. No. 9,663,649, can be used to impart flame retardancy tosolid foams, and flame retardants can be incorporated into the foamusing a masterbatch composition. However, the ultimate flame retardancyperformance of the brominated compounds in such foams can depend on thethermal stability of the bromine-carbon bonds. That is, these bonds mustbe stable enough to endure the temperatures encountered during thevarious manufacturing processes that may be used in formulating themasterbatch composition initially, or in combining the masterbatchcomposition into a separate resin or foam composition, or further in theactual making of an article comprising the resin or foam compositioncontaining the masterbatch composition. It is desirable for thebrominated FR additive composition to not be appreciably negativelyaffected by these manufacturing steps, which can include exposure totemperatures in excess of 200° C. This helps ensure the brominated FRadditive composition performs as intended, that is, it retains adequatebromine that can be released as an active bromine-containing species tohelp suppress flames under fire conditions if the final articlecontaining the masterbatch composition experiences a thermal event(e.g., to 250° C. or a higher temperature).

Generally, masterbatch composition manufacturing processes, or processesthat combine the masterbatch composition into a resin or foamcomposition, are melt processes and occur in an organic phase. If thebrominated FR additive is not adequately thermally stable, bromine canbecome liberated during these processes. This bromine can form the acidhydrogen bromide (HBr) that can corrode processing equipment, furthercatalytically degrade the FR additive, and present concerns about workerexposure. To mitigate this acid formation, organically soluble acidscavengers, such as epoxy-based acid scavengers, are added to thebrominated FR additive masterbatch composition to manage this acid inthe organic phase.

However, in many final foam formulations, including formulationscomprising styrene-acrylonitrile (SAN) copolymers, water is used as aco-blowing agent. The mobility of the HBr is high in the aqueous phaseand the HBr can drive undesirable kinetics of dehydrohalogenationreactions, including undesirable viscosity increases via cross linkingof the SAN copolymers also known as SAN hydrolysis.

What is needed is a water soluble pH moderator that can be included inthe brominated FR additive masterbatch composition, that can survive themelt processes of manufacturing the masterbatch composition and furtherprocessing of the masterbatch composition into a resin or foamcomposition, and that can further be available as a pH moderator whenwater is present, particularly when water is used as a co-blowing agentto make a foam. In particular, what is needed is a water soluble pHmoderator that will not negatively impact the foam-forming process orthe appearance of the resulting foam as evidenced by the Yellow Index;and that further slows the induction time for kinetics of sidechemistries in that foam composition, as evidenced by the degradationonset time of the foam or masterbatch by thermogravimetric analysis(TGA).

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a masterbatch composition suitable foruse as a flame retardant in extruded polymer foams, comprising:

-   -   (a) 20 to 40 parts by weight base resin comprising styrene        homopolymer or copolymer;    -   (b) 1 to 16 parts by weight acid scavenger comprising an        epoxy-based compound;    -   (c) 2 to 6 parts by weight antioxidant comprising an alkyl or        aryl phosphite; and    -   (d) 45 to 60 parts by weight flame retardant comprising a        non-hexabromocyclododecane (HBCD) brominated polymer or        copolymer;    -   wherein the amounts of (a), (b), (c), and (d) total 100 parts by        weight;    -   the masterbatch composition further comprising    -   (e) 0.6 to 10 parts by weight of water soluble pH moderator,        based on 100 parts of base resin plus the at least one water        soluble pH moderator.

The present invention also relates to an extruded polymer foamcomprising a masterbatch composition, the masterbatch compositioncomprising:

-   -   (a) 20 to 40 parts by weight base resin comprising styrene        homopolymer or copolymer;    -   (b) 1 to 16 parts by weight acid scavenger comprising an        epoxy-based compound;    -   (c) 2 to 6 parts by weight antioxidant comprising an alkyl or        aryl phosphite; and    -   (d) 45 to 60 parts by weight flame retardant comprising a        non-hexabromocyclododecane (HBCD) brominated polymer or        copolymer;    -   wherein the amounts of (a), (b), (c), and (d) total 100 parts by        weight;    -   the masterbatch composition further comprising    -   (e) 0.6 to 10 parts by weight of a water soluble pH moderator,        based on 100 parts of (a) base resin plus (e) water soluble pH        moderator.

The present invention further relates to a process for manufacturing amasterbatch composition suitable for use as a flame retardant inextruded polymer foams, comprising the steps of:

-   -   a) providing a base resin to a mixing device operating at        temperature of 150 to 230° C. to form a molten base resin;    -   b) contacting the molten base resin in the mixing device with:        -   i) acid scavenger comprising one or more epoxy-based            compounds;        -   ii) antioxidant comprising an alkyl or aryl phosphite;        -   iii) water soluble pH moderator; and        -   iv) flame retardant comprising a            non-hexabromocyclododecane(HBCD) brominated polymer or            copolymer    -    to form a molten flame retardant masterbatch composition; and    -   c) cooling the molten flame retardant masterbatch composition to        form a solid flame retardant masterbatch composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one possible process for making pellets ofa masterbatch composition using a twin-screw extrusion line.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a more environmental-friendlymasterbatch composition suitable for use as a flame retardant inextruded polymer foams, the masterbatch comprising (a) base resincomprising styrene homopolymer or copolymer; (b) acid scavengercomprising an epoxy-based compound; (c) antioxidant comprising an alkylor aryl phosphite; (d) flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer and(e) water soluble pH moderator.

By “masterbatch composition”, it is meant that the composition can beused as an additive in resins and foams.

By “flame retardant” it is meant that an ingredient has the ability toincrease the Limiting Oxygen Index (LOI) values of melt-fabricatedarticles, such as foams, fibers, films, etc., thereby enabling sucharticles to pass standard fire tests. Air contains approximately 21%oxygen and therefore any material with a LOI value of 21 or less willlikely burn in air. Specifically, for the purposes herein, an ingredientis considered a flame retardant if its presence in a composition orformulation can increase the LOI of the article to 24 or greater. ALimiting Oxygen Index of 24 or greater enables many foam articles topass standard fire tests, such as Underwriters Laboratory (UL) 723 andEuropean Norm (EN) Fire Test # ISO 11925-2 Class E, and North Americanbuilding code standards for C578 and S701.

(a) Base Resin

The masterbatch composition comprises base resin that is used primarilyas a carrier resin for compounding the flame retardant with the otheradditives. The base resin comprising styrene homopolymer or copolymer ispresent in the masterbatch composition in an amount of 20 to 40 parts byweight, based on the total amount in the masterbatch composition of (a)base resin comprising styrene homopolymer or copolymer, (b) acidscavenger comprising an epoxy-based compound; c) antioxidant comprisingan alkyl or aryl phosphite; and (d) flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer.

For the purposes herein, it is understood the “base resin comprisingstyrene homopolymer or copolymer” as recited herein could be one or moreresin(s) comprising styrene homopolymer or copolymer, and the amount of“base resin comprising styrene homopolymer or copolymer” is consideredto be the total amount of resin(s) comprising styrene homopolymer orcopolymer in the masterbatch composition, separate from any flameretardant polymers comprising styrene homopolymer or copolymer. Also,for the purposes herein regarding the amounts of ingredients in themasterbatch, the base resin(s) comprising styrene homopolymer orcopolymer is(are) considered separate from the flame retardant(s)comprising non-hexabromocyclododecane (HBCD) brominated polymer orcopolymer.

It is believed that having less than 20 parts by weight of the baseresin in the masterbatch composition can raise the viscosity and melttemperature of the masterbatch, particularly above 230° C., which canlead to increased thermal decomposition because of shear heating. Also,the presence of the base resin helps disperse the ingredients into themasterbatch, and if too little base resin is present, the flameretardant may not be adequately dispersed and will instead form largedomains of flame retardant in the masterbatch. This in turn cannegatively impact the ability of acid scavenger(s), the antioxidant(s),and pH moderator(s) to effectively protect the flame retardant. Morethan 40 parts by weight of the base resin in the masterbatch compositionis undesirable because this unnecessarily increases the manufacturingcost of masterbatch. In some embodiments, the base resin comprisingstyrene homopolymer or copolymer is present in the masterbatchcomposition in an amount of 26 to 35 parts by weight, based on the totalamount of components (a), (b), (c), and (d) described previously.

Some preferred base resins include polystyrene homopolymers, andcopolymers of styrene with ethylene, propylene, acrylic acid, maleicanhydride, and/or acrylonitrile. Polystyrene homopolymer is mostpreferred. Blends of any two or more of the foregoing polymers, or ofone or more of the foregoing polymers with another resin, also can beused as the base resin.

In some embodiments, base resins of styrene/butadiene copolymers areespecially preferred. Some styrene/butadiene block copolymers that areuseful as the starting polymer include those available from DexcoPolymers under the trade designation VECTOR™. Styrene/butadiene randomcopolymers may be prepared in accordance with the processes described byA. F. Halasa in Polymer, Volume 46, page 4166 (2005). Styrene/butadienegraft copolymers may be prepared in accordance with methods described byA. F. Halasa in Journal of Polymer Science (Polymer Chemistry Edition),Volume 14, page 497 (1976). Styrene/butadiene random and graftcopolymers may also be prepared in accordance with methods described byHsieh and Quirk in chapter 9 of Anionic Polymerization Principles andPractical Applications, Marcel Dekker, Inc., New York, 1996. A startingpolymer may also contain repeating units formed by polymerizing monomersother than butadiene and a vinyl aromatic monomer. Such other monomersinclude olefins such as ethylene and propylene, acrylate or acrylicmonomers such as methyl methacrylate, methyl acrylate, acrylic acid, andthe like. These monomers may be randomly polymerized with the vinylaromatic monomer and/or butadiene, may be polymerized to form blocks, ormay be grafted onto the starting butadiene copolymer. The most preferredtype of starting butadiene polymer is a block copolymer containing oneor more polystyrene blocks and one or more polybutadiene blocks. Amongthese, di-block and tri-block copolymers are especially preferred.

(b) Acid Scavenger

Acid scavenger(s) comprising an epoxy-based compound is(are) present inthe masterbatch composition in an amount of 1 to 16 parts by weight,based on the total amount in the masterbatch composition of (a) baseresin comprising styrene homopolymer or copolymer, (b) acid scavengercomprising an epoxy-based compound; c) antioxidant comprising an alkylor aryl phosphite; and (d) flame retardant(s) comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer.

For the purposes herein, it is understood the “acid scavenger comprisingan epoxy-based compound” as recited herein could be one or more acidscavenger(s) comprising an epoxy-based compound, and the amount of “acidscavenger comprising an epoxy-based compound” is considered to be thetotal amount of acid scavenger(s) comprising an epoxy-based compound inthe masterbatch composition.

It is believed that less than 1 part by weight acid scavenger in themasterbatch composition will not provide adequate acid scavengingperformance for the masterbatch, and the more than 20 parts by weightacid scavenger in the masterbatch composition is undesirable not onlybecause higher amounts do not provide appreciable benefit commensuratewith the increased cost, but also higher amounts can cause masterbatchpellets to stick together. In some embodiments, the acid scavenger ispresent in the masterbatch composition in an amount of 4-10 parts byweight, based on the total amount of components (a), (b), (c), and (d)described previously.

Further, from 3 to 11 parts by weight of the acid scavenger are presentper 100 parts by weight of the flame retardant in the masterbatchcomposition. In some embodiments, 4 to 7 parts by weight of the acidscavenger are present per 100 parts by weight of the flame retardant inthe masterbatch composition. In some embodiments, 8 to 10 parts byweight of the acid scavenger are present per 100 parts by weight of theflame retardant in the masterbatch composition.

In some embodiments, the epoxy compound contains on average at least oneand preferably two or more epoxide groups per molecule. The epoxycompound preferably has an equivalent weight per epoxide group of nomore than 2000, preferably no more than 1000 and even more preferably nomore than 500. The molecular weight of the epoxy compound is at least1000 in some preferred embodiments. The epoxy compound can further bebrominated. A variety of commercially available epoxy resins aresuitable. These may be based, for example, on a bisphenol compound, suchas various diglycidyl ethers of bisphenol A. They may be based on abrominated bisphenol compound. The epoxy compound may be an epoxynovolac resin, or an epoxy cresol novolac resin. The epoxy compound maybe an entirely aliphatic material, such as a diglycidyl ether of apolyether diol or an epoxidized vegetable oil. Examples of commerciallyavailable epoxy compounds that are useful herein include F2200HM andF2001 (from ICL Industrial Products), DEN 439 (from The Dow ChemicalCompany), Araldite ECN-1273 and ECN-1280 (from Huntsman AdvancedMaterials Americas, Inc.), and Plaschek 775 (from Valtris SpecialtyChemicals).

In some preferred embodiments, the acid scavenger comprises an epoxycresol novolac resin. In some other preferred embodiments, the acidscavenger comprises epoxidized oil. In some other preferred embodiments,epoxy cresol novolac resin and epoxidized oil are both present in themasterbatch composition as acid scavengers. In some other preferredembodiments, the acid scavenger in the composition comprises a majorityof epoxidized oil; that is, more than 50 weight percent of the epoxycompound present in the masterbatch composition is in the form ofepoxidized oil.

(c) Antioxidant

The masterbatch composition includes at least one antioxidant forstabilizing radicals formed during manufacture of the masterbatchcomposition and later incorporation of the masterbatch composition in asubsequent foam composition. These undesirable radicals can lead toundesirable color formation and crosslinking that can foul foamingprocess equipment, requiring downtime for cleaning.

The antioxidant comprising an alkyl or aryl phosphite is present in themasterbatch composition in an amount of 2 to 6 parts by weight, based onthe total amount in the masterbatch composition of (a) base resincomprising styrene homopolymer or copolymer, (b) acid scavengercomprising an epoxy-based compound; (c) antioxidant comprising an alkylor aryl phosphite; and (d) flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer.

For the purposes herein, it is understood the “antioxidant comprising analkyl or aryl phosphite” as recited herein could be one or moreantioxidant(s) comprising an alkyl or aryl phosphite, and the amount of“antioxidant comprising an alkyl or aryl phosphite” is considered to bethe total amount of antioxidant(s) comprising an alkyl or aryl phosphitein the masterbatch composition.

It is believed that less than 2 parts by weight antioxidant in themasterbatch composition will not provide adequate inhibition ofundesirable oxidation reactions, and that more than 6 parts by weightantioxidant in the masterbatch composition is undesirable because thisadds cost without appreciable benefit. In some embodiments, theantioxidant comprising an alkyl or aryl phosphite is present in themasterbatch composition in an amount of 3-4.5 parts by weight, based onthe total amount of components (a), (b), (c), and (d) describedpreviously.

Suitable alkyl phosphites are described in U.S. Pat. No. 9,663,649 toKram et al. Specific examples of preferred alkyl phosphites include bis(2,4-dicumylphenyl)pentaerythritol diphosphite, distearylpentaerythritoldiphosphite and di(2,4-di-(t-butyl)phenyl) pentaerythritol diphosphite.These are commercially available as Doverphos™ S-9228 (Dover ChemicalCorporation), Doverphos™ S-682 (Dover Chemical Corporation) and Irgafos™126 (Ciba Specialty Chemicals).

Suitable aryl phosphites are described in PCT Publication No.WO2014/174704 to Huang et al. Specific examples of some preferred arylphosphites include substituted aryl phosphites. One specific suchpreferred aryl phosphite is tris(2,4-di-tert-butylphenyl)phosphite,commercially available under the name Irgafos™ 168. If desired, amixture of both alkyl and aryl phosphites can be used together in themasterbatch.

Further, from 3 to 11 parts by weight of the antioxidant are present per100 parts by weight of the flame retardant in the masterbatchcomposition. In some embodiments, 4 to 7 parts by weight of theantioxidant are present per 100 parts by weight of the flame retardantin the masterbatch composition. In some embodiments, 8 to 10 parts byweight of the antioxidant are present per 100 parts by weight of theflame retardant in the masterbatch composition.

(d) Flame Retardant

The flame retardants used in the masterbatch composition arenon-hexabromocyclododecane (HBCD) brominated polymers and copolymers.These are considered more environmental responsible replacements forHBCD, a commonly used flame retardant for polystyrene foams that hasexperienced governmental regulatory issues due to bioaccumulationconcerns.

In some embodiments, preferred flame retardants used in the masterbatchcomposition are thermally stable brominated copolymers such as abrominated styrene/butadiene block copolymer (Br-SBC), brominated randomstyrene/butadiene copolymer (Br-r-SB), or brominated styrene/butadienegraft copolymer (Br-g-SB) such as disclosed in U.S. Pat. No. 7,851,558to King et al.

In some embodiments, a preferred non-HBCD brominated polymer orcopolymer flame retardant has the following structure and iscommercially available from the DuPont Company, Inc under that nameBLUEDGE™ polymeric flame retardant (PFR) and is also available asEmerald Innovation™ 3000 and FR122P.

Some other suitable non-HBCD brominated polymer or copolymer flameretardants are disclosed in “Flame Retardant Alternatives ForHexabromocyclododecane (HBCD)—Final Report” (June 2014) by the UnitedStates Environmental Protection Agency. One class of non-HBCD brominatedflame retardants mentioned in the report was TBBPA-bis brominated etherderivatives, such as those having the chemical name of(1,1′-(1-methylethylidene)bis[3,5-dibromo-4-(2,3-dibromo-2-methylpropoxy)]benzene) that is commercially available under the names of PYROGUARDSR-130 and SR-130. Another class of non-HBCD brominated flame retardantsmentioned in the report was TBBPA bis(2,3-dibromopropyl) ethers, such asthose having the chemical name of(:1,1′-(1-methylethylidene)bis[3,5-dibromo-4-(2,3-dibromopropoxy)]benzene) commercially available under the names of PYROGUARD SR 720 andSR 720. While each of the non-HBCD brominated flame retardants can beused by themselves in the masterbatch, in some instances it may bedesirable to have a mixture of these non-HBCD brominated flameretardants in the masterbatch.

In some embodiments, the flame retardant used in the masterbatchcomposition comprises brominated styrene/butadiene block copolymer inwhich fewer than 1% of the carbon-bromine bonds are at allylic ortertiary carbons. Further, in a preferred embodiment, the amount offlame retardant used in the masterbatch composition should be sufficientto provide an extruded polymer foam composition, to which themasterbatch has been added, 0.35 to 5 weight percent bromine. In someembodiments, the amount of flame retardant used in the masterbatchcomposition should be sufficient to provide an extruded polymer foamcomposition 1.0 to 2.5 weight percent bromine.

Further, while the total amount of masterbatch added to a foamcomposition can vary over a wide range, depending on such things as thetype of foam, the desired foam application, and the inclusion of otheradditives, it is desirable in many instances that the masterbatch bepresent in the final foam in an amount that ranges from about 0.5 toabout 7.6 weight percent, based on the total combined weight of the foamplus the masterbatch. In some embodiments, the masterbatch is present inthe final foam in amounts of about 0.6 to 4 weight percent, based on thetotal combined weight of the foam plus the masterbatch; while in otherembodiments, the masterbatch is present in the final foam in amountsfrom about 3 to 7.6 weight percent based on the total combined weight ofthe foam plus the masterbatch.

The non-HBCD brominated polymer or copolymer flame retardant is presentin the masterbatch composition in an amount of 45 to 60 parts by weight,based on the total amount in the masterbatch composition of (a) baseresin comprising styrene homopolymer or copolymer, (b) acid scavengercomprising an epoxy-based compound; c) antioxidant comprising an alkylor aryl phosphite; and (d) flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer.

For the purposes herein, it is understood the “flame retardantcomprising non-hexabromocyclododecane (HBCD) brominated polymer orcopolymer” as recited herein could be one or more flame retardant(s)comprising non-hexabromocyclododecane (HBCD) brominated polymer orcopolymer, and the amount of “flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer” isconsidered to be the total amount of flame retardant(s) comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer in themasterbatch composition. Also, for the purposes herein regarding theamounts of ingredients in the masterbatch, the flame retardant(s)comprising non-hexabromocyclododecane (HBCD) brominated polymer orcopolymer is(are) considered separate from the base resin(s) comprisingstyrene homopolymer or copolymer.

Approximately 45 parts by weight of the non-HBCD brominated polymer orcopolymer flame retardant in the masterbatch composition is considered apractical minimum for a desirable masterbatch composition suitable foruse in many applications. It is believed that less than this amount maystill provide some flame retardancy, but not at the level required bymany FR standards, meaning additional flame retardants will have to beseparately added to the final foam composition to meet those standards,essentially defeating the value of having a single flame retardantmasterbatch composition. Further, more than 60 parts by weight of thenon-HBCD brominated polymer or copolymer flame retardant in themasterbatch composition is undesirable. Such masterbatches, having ahigh concentration of flame retardant, are not only susceptible tothermal decomposition from shear heating, but also have a higherviscosity making them more difficult to disperse in foam formulations.The 45 to 60 parts by weight of the non-HBCD brominated polymer orcopolymer flame retardant in the masterbatch provides a bromine loadingof approximately 29 to 40% bromine to the masterbatch. In someembodiments, the non-HBCD brominated polymer or copolymer flameretardant is present in the masterbatch composition in an amount of 50to 55 parts by weight, based on the total amount of components (a,),(b), (c), and (d) in the masterbatch described previously.

(e) Water Soluble pH Moderator

The masterbatch composition further comprises 0.6 to 10 parts by weightof water soluble pH moderator, based on 100 parts of (a) base resin plus(e) water soluble pH moderator. In some embodiments, the masterbatch hasa minimum of 1 part by weight water soluble pH moderator and a maximumof 10 parts by weight water soluble pH moderator, based on 100 parts of(a) base resin plus (e) water soluble pH moderator. In some otherembodiments, the masterbatch has a minimum of 1.5 parts by weight watersoluble pH moderator and a maximum of 10 parts by weight water solublepH moderator, based on 100 parts of (a) base resin plus (e) watersoluble pH moderator.

For the purposes herein, it is understood the “water soluble pHmoderator” as recited herein could be one or more water soluble pHmoderator(s), and the amount of “water soluble pH moderator” isconsidered to be the total amount of water soluble pH moderator(s) inthe masterbatch composition.

It is believed that less than 0.6 parts by weight water soluble pHmoderator will not provide adequate stabilizing performance for themasterbatch, and that more than 10 parts by weight water soluble pHmoderator is undesirable because higher quantities can build up on diesand affect foam quality. In some embodiments, the masterbatchcomposition comprises 5 to 10 parts by weight of a water soluble pHmoderator, and in some embodiments 6 to 10 parts by weight of a watersoluble pH moderator, again based on 100 parts of (a) base resin plus(e) water soluble pH moderator. In some other embodiments, themasterbatch composition comprises 1.5 to 5 parts by weight of a watersoluble pH moderator, again based on 100 parts of (a) base resin plus(e) water soluble pH moderator.

By “water soluble” it is meant that the pH moderator has a solubility inroom temperature (20° C., 68° F.) water of at least 20 grams per liter.Preferably, the water soluble pH moderator has a solubility in roomtemperature (20° C., 68° F.) water of at least 90 grams per liter. Thislevel of solubility ensures the pH moderator will be adequatelyavailable when contacted with an acidic species in an aqueous phase inthe foam making process.

Further, in some embodiments, the preferred water soluble pH moderatorsare those that do no form undesirable byproducts in the masterbatch orfoam after reacting with free hydrogen bromide. In some most preferredembodiments, the water soluble pH moderators are compounds that reactwith hydrogen bromide and essentially form only salts as byproducts. Forexample, sodium carbonate reacts with HBr to form sodium bromide andsodium bicarbonate. Likewise, sodium bicarbonate reacts with HBr to formsodium bromide, carbon dioxide, and water. In some other embodiments,suitable water soluble pH moderators are compounds that react withhydrogen bromide and essentially form only salts or weak acids asbyproducts. For example, sodium borates such as sodium tetraboratedecahydrate form sodium bromide and very weak boric acids.

In some embodiments, the water soluble pH moderator is sodium carbonate,sodium bicarbonate, or a borate such as sodium tetraborate decahydrate.In some preferred embodiments, the water soluble pH moderator is sodiumcarbonate, commonly known as soda ash. The use of soda ash has severalunexpected benefits. First, while soda ash is a weak base, it has foundthat it has sufficient alkalinity and reaction kinetics to effectivelyneutralize the strong acid HBr that is generated by the degradation ofthe carbon-bromide bond from the backbone of the brominated flameretardants.

Second, the soda ash can be well dispersed in the polymer and does nothave a major negative effect on foaming processes in which themasterbatch composition is used. No process issues such as die buildup,or surface defects on the resultant foams were observed.

Third, the soda ash is highly soluble in water and ultimately generatesby-products of H₂O and CO₂ which are common to many foam processes asblowing agents so the soda ash is a gentle volatile additive in theprocess.

Finally, it was unexpectantly found that the addition of soda ashallowed a reduction in the amount of higher-cost organic epoxide acidscavengers needed in the composition, as evidenced by similar TGAdegradation onset times for the masterbatch and foam when a portion ofthe acid scavenger was replaced by the pH moderator.

While the epoxy-based acid scavengers are organic and can manage acidicspecies in the organic phase, the addition of a water soluble pHmoderator can help maintain the pH in the aqueous phase, where themobility of an acidic species like HBr is high and can rapidly drive thekinetics of dehydrohalogenation reactions. In particular, the use ofsoda ash significantly impacts the induction time for kinetics of sidechemistries which can lead to undesirable viscosity increases via crosslinking in formulations comprising styrene-acrylonitrile (SAN)copolymers.

Further, it is unexpected that suitable foams can be made with a flameretardant masterbatch comprising 0.6 to 10 parts by weight water solublepH moderator, based on 100 parts of (a) base resin plus (e) watersoluble pH moderator, particularly since the stabilizer is an inorganicmaterial. The conventional wisdom is that inorganic materials, even ifused in even minor amounts, can form deposits on processing surfaces andslough off, creating defects in the masterbatch or foam. Further, theseundesirable deposits have an extended heat history that can reduce thethermal stability of the masterbatch and foam. Therefore, one would notexpect that any of the suitable amounts of water soluble pH moderatordiscussed herein would be able to provide the perfectly suitable foamsthat have been made.

Process for Making Masterbatch Composition

The present invention further relates to a process for manufacturing amasterbatch composition suitable for use as a flame retardant inextruded polymer foams, comprising the steps of:

-   -   a) providing a base resin to a mixing device operating at        temperature of 150 to 230° C. to form a molten base resin;    -   b) contacting the molten base resin in the mixing device with:        -   i) acid scavenger comprising one or more epoxy-based            compounds;        -   ii) antioxidant comprising an alkyl or aryl phosphite;        -   iii) water soluble pH moderator; and        -   iv) flame retardant comprising a non-hexabromocyclododecane            (HBCD) brominated polymer or copolymer    -    to form a molten flame retardant masterbatch composition; and    -   c) cooling the molten flame retardant masterbatch composition to        form a solid flame retardant masterbatch composition.

In some embodiments, the process for manufacturing a masterbatchcomposition suitable for use as a flame retardant in extruded polymerfoams can further include the step of:

-   -   d) pelletizing the solid flame retardant masterbatch composition        to form pellets.

The process for manufacturing a masterbatch composition suitable for useas a flame retardant in extruded polymer foams comprises combining andmixing together a number of ingredients, including base resin, flameretardant, antioxidant, acid scavenger, and water soluble pH moderatorat a temperature suitable for making a molten mixture of themasterbatch, and then cooling that molten composition to form a solid.The solid is then optionally formed into pellets.

The mixing can be achieved in any device that can provide (or maintain)the ingredients with (at) a suitable elevated temperature such that thebase resin and organic additives melt, and all the ingredients aresuitably uniformly dispersed in the melt phase. Generally, it isadvantageous to melt a quantity of the base resin as a carrier and thenadd the other ingredients, either singly or in mixtures. As such,typically extruders, specifically twin-screw extruders and variants thatuse a screw-type or other mixing elements such as a Farrel continuousmixer are preferred, as continuous production of the masterbatch ispossible. However, the mixing can be conducted in a batch mode using anytype of mixture capable of operating at an elevated temperature.

In a preferred process, a base resin as previously described herein isprovided in pellet or powder form to a mixing device, such as atwin-screw extruder, operating at a temperature of about 150 to 230° C.,which forms a molten base resin. The base resin, and any of the otheringredients that are in pellet or powder form, can be metered into theextruder using weigh feeders or hoppers designed to supply the extruder,or other even devices such as feeder extruders. Ingredients in liquidform can be supplied to the extruder using either metering pumps orvarious pumping and metering devices.

The molten base resin in the mixing device is then contacted with atleast one acid scavenger comprising one or more epoxy-based compounds,at least one antioxidant and at least one water soluble pH moderator.

In some preferred processes, the acid scavenger is an epoxidized oil oran epoxy cresol novolac resin. In some especially preferred processesthe molten base resin is contacted with both an epoxidized oil and anepoxy cresol novolac resin. This can be accomplished sequentially byseparate additions, as the oil is a liquid and the resin can be inpellet or powder form. In some embodiments where the epoxidized oil isused, it is preferably the majority of the acid scavenger used in theprocess, as the oil provides some additional lubricating quality to theextrusion process.

The antioxidant and the water soluble pH moderator are generally addedto the composition in small quantities, while the flame retardantgenerally forms the majority component in the masterbatch. While each ofthese ingredients can be added separately to the mixing device, but itcan be advantageous to first mix the solid (powder and/or pellet)ingredients together and then add this mixture to the mixing device.

The antioxidant comprises an alkyl or aryl phosphite as previouslydescribed herein. The water soluble pH moderator is as previouslydescribed herein and is preferably soda ash, added in an amount that is0.6 to 10 parts by weight of a water soluble pH moderator, based on 100parts of base resin plus pH moderator.

After suitable mixing to form a uniform molten masterbatch composition,the molten flame retardant masterbatch composition is cooled to form asolid masterbatch composition. If the mixer is an extruder, generallythe molten masterbatch composition is extruded through a die intostrands of molten material that are cooled into solid strands. The solidmasterbatch can in turn be optionally made into masterbatch pellets. Onesuitable method of cooling the molten flame retardant masterbatchcomposition is by extruding the composition through a die, followed byquenching the strands via the use of one or more water baths; thequenched strands can be further directed to a pelletizer such as anunderwater pelletizer if masterbatch pellets are desired. Preferably thepellets are sized such that there are 25 to 40 pellets per gram.

One possible manufacturing process for the flame retardant masterbatchcomposition is shown in FIG. 1. A twin-screw extruder 10 maintained atelevated temperature is provided with polystyrene pellets via a feeder1. As generally a small amount of solid epoxy cresol novolac resin istypically used, a mixture of polystyrene and epoxy cresol novolac resinpellets or powders can be formed and introduced into the extruder via afeeder 2. In this process, a liquid epoxidized oil is next metered intothe extruder via an injector 3. Finally, in this process a mixture ofthe flame retardant, antioxidant, and water soluble pH moderator areadded via a side feeder 4.

The twin-screw extruder the extrudes the molten flame retardantmasterbatch composition through a die into strands, which are quenchedin water bath 20; the quenched strands are then directed to pelletizer30 to form masterbatch pellets 40.

As illustrated by FIG. 1, in one process for manufacturing themasterbatch composition, preferably at least one of the at least oneacid scavenger, the at least one antioxidant, or the water soluble pHmoderator contacts the molten base resin in the mixing device prior tothe flame retardant contacting the base resin. In an especiallypreferred process for manufacturing the masterbatch composition, atleast one acid scavenger contacts the molten base resin in the mixingdevice prior to the flame retardant contacting the base resin. Thisprovides a base resin that has pre-loaded protective ingredients thathelp prevent thermal degradation of the flame retardant during theentire time it is at an elevated temperature.

Further, as previously discussed herein, preferably the process formanufacturing the masterbatch composition comprises providing (a) 20 to40 parts by weight of at least one base resin comprising styrenehomopolymer or copolymer to a mixing device operating at temperature of150 to 230° C. to form a molten base resin, followed by contacting thebase resin with (b) 1 to 16 parts by of at least one weight acidscavenger comprising an epoxy-based compound, (c) 2 to 6 parts by weightof at least one antioxidant comprising an alkyl or aryl phosphite; and(d) flame retardant comprising a non-hexabromocyclododecane (HBCD)brominated polymer or copolymer; wherein the amounts of (a), (b), (c),and (d) total 100 parts by weight; the masterbatch composition furthercomprising (e) 0.6 to 10 parts by weight of a water soluble pHmoderator, based on 100 parts of (a) at least one base resin plus (e)water soluble pH moderator.

Extruded Foams

The present invention further relates to extruded polymer foamscomprising a masterbatch composition suitable for use as a flameretardant in extruded polymer foams, the masterbatch comprising (a) baseresin comprising styrene homopolymer or copolymer; (b) acid scavengercomprising an epoxy-based compound; (c) antioxidant comprising an alkylor aryl phosphite; (d) flame retardant comprisingnon-hexabromocyclododecane (HBCD) brominated polymer or copolymer and(e) water soluble pH moderator.

Extruded foams can be made using many different processes, includingthose such as disclosed in Kram et al., U.S. Pat. No. 9,517,579. Theflame retardant masterbatch composition is especially useful in themanufacture of foam boards such as those made in large quantities fromstyrenic polymers in a melt extrusion process. Such extrusion foamingprocesses are performed by forming a pressurized melt that contains thepolymer(s) to be foamed, which collectively are referred to herein asthe bulk polymer, the masterbatch composition suitable for use as aflame retardant as described herein, and a blowing agent; and otheradditives such as may be useful. One advantage, however, of the use ofthe present masterbatch is that preferably only the bulk polymer,masterbatch, and blowing agent are required.

The bulk polymer and the masterbatch are conveniently provided to thefoam processing apparatus in the form of pellets or other smallparticulates, which are melted in the foam processing apparatus. Themasterbatch may be pre-blended or added simultaneously with the bulkpolymer to the foam processing apparatus, in which case the bulk polymerand the masterbatch are concurrently melted in the foam processingapparatus. Alternatively, the masterbatch can be added to foamprocessing apparatus after the bulk polymer, in which case the bulkpolymer is either partially or fully molten. The foam processingapparatus should be of suitable capacity and the rate of processingshould be adequate to fully melt and disperse the flame retardantmasterbatch uniformly in the bulk polymer.

It is generally preferred to introduce the blowing agent as a separatestream after the polymeric materials have been melted. The blowing agentin an extrusion foaming process can be an exothermic (chemical) type oran endothermic (physical) type. Physical blowing agents such as carbondioxide, various hydrocarbons, hydrofluorocarbons, water, alcohols,ethers and hydrochlorofluorocarbons are especially suitable.

While the present flame retardant masterbatch having a water soluble pHmoderator is especially useful when water is used as at least one of theblowing agents, the water soluble pH moderator is also effective whenwater is not the blowing agent, as many of the ingredients are nottotally free of moisture and most processing equipment is not inerted toprevent water from being absorbed by the materials during the extrusionfoaming process.

In one embodiment, the blowing agent is a mixture, and that mixture caninclude carbon dioxide, ethanol and water. In another embodiment, theblowing agent can include carbon dioxide, ethanol, a C₄-C₅ hydrocarbon,and water. The C₄-C₅ hydrocarbon is preferably isobutane. Preferably,total amount of blowing agent is employed in an amount sufficient toprovide the extruded foam with a foam density of no greater than 40kg/m³, more preferably no greater than 36 kglm³ and still morepreferably no greater than 35 kg/m³. It is believed these densities arebest achieved when the total amount of blowing agent is within the rangeof from about 1.1 to about 1.8 moles of blowing agent per kilogram ofthe bulk polymer. In some instances, a preferred total amount of blowingagent is from 1.1 to about 1.7 moles per kilogram of the bulk polymer. Astill more preferred amount is from 1.15 to 1.65 moles per kilogram ofthe bulk polymer. Individually, carbon dioxide is preferably used in anamount from about 0.5 to about 1.2 moles per kilogram of the bulkpolymer, more preferably from 0.65 to about 0.9 moles per kilogram ofthe bulk polymer. Ethanol is preferably used in an amount of from 0.15to 0.5 moles per kilogram of the bulk polymer, more preferably from 0.25to 0.45 moles per kilogram of the bulk polymer. Water is preferably usedin an amount of from about 0.1 to about 0.4 moles per kilogram of thebulk polymer, more preferably from 0.1 to 0.3 moles per kilogram of thebulk polymer. The C₄-C₅ hydrocarbon is preferably present in an amountof up to 0.35 moles per kilogram of the bulk polymer, and morepreferably from 0.1 to 0.3 moles per kilogram of the bulk polymer.

In one embodiment, the blowing agent contains a combination, perkilogram of the bulk polymer, of 0.65 to 0.9 moles carbon dioxide, 0.25to 0.45 moles ethanol and from 0.1 to 0.3 moles water, with the totalamount of blowing agent being from 1.1 to 1.65 moles per kilogram of thebulk polymer. In another embodiment the blowing agent combinationcontains, per kilogram of the bulk polymer, 0.65 to 0.9 moles carbondioxide, 0.25 to 0.45 moles ethanol, 0.1 to 0.3 moles of isobutene, andfrom 0.1 to 0.3 moles of water, with the total amount of blowing agentbeing from 1.15 to 1.65 moles per kilogram of the bulk polymer.

Once the bulk polymer, masterbatch, and other optional additives havebeen mixed and the polymers melted and further mixed with the blowingagent(s), the resulting gel is forced through an opening into a zone oflower pressure, where the blowing agent expands and the polymersolidifies to form an extruded foam.

Foams produced in this manner preferably have a density of up to 80kg/m³, more preferably up to 64 kg/m³, and even more up to 48 kg/m³.Foam used as thermal insulation is preferably in the form of boardstockhaving a density of from 24 to 48 kg/m³. Billet foam preferably has adensity of from 24 to 64 kg/m³, more preferably from 28 to 48 kg/m³. Thefoams preferably have an average cell size in the range of from 0.1 mmto 4.0 mm, especially from 0.1 to 0.8 mm, as determined per ASTM D3576.The foam may be predominantly closed-celled, i.e., may contain 30% orless, preferably 10% or less and even more preferably 5% or less of opencells, as determined per ASTM D6226-05. More open-celled foams can alsobe produced in accordance with the invention. Boardstock foams made inaccordance with the invention are useful as building foam insulation, aspart of roof or wall assemblies. Other foams made in accordance with theinvention can be used as decorative billet, pipe insulation and inmolded concrete foundation applications.

Test Methods

Degradation Onset Time of Brominated Polymeric Concentrate byThermogravimetric Analysis (TGA). TGA is a method of thermal analysis inwhich changes in physical and chemical properties of materials aremeasured as a function of increasing temperature (with constant heatingrate), or as a function of time (with constant temperature and/orconstant mass loss). TGA is commonly used to determine selectedcharacteristics of materials that exhibit either mass loss or gain dueto decomposition, oxidation, or loss of volatiles (such as moisture).After the sample is loaded, it holds isothermal at 25° C. for 5 minutesunder nitrogen, and ramps at 25° C./min to 235° C. It keeps isothermalat 235° C. for 60 minutes and then cools down to 30° C. The TGA onsettime is defined as the time when significant degradation begins(inflection point).

Yellow Index (YI) Measurement. Yellow index (YI) is measured accordingto ASTM E315-15. The samples is measured by a spectrophotometer ortri-stimulus (filter) colorimeter. Values of X, Y.Z for each measurementare measured, and if multiple measurements are made of a single specimenand set of conditions, average values of X, Y, Z are provided. Forpellets, YI should be less than 75; for plaques, YI should be less than40.

The glass transition temperature (Tg) Onset Temperature. Samples with amass of 5 to 10 mg were cut from a pellet, weighed, and sealed inaluminum DSC pans for analysis. The samples were scanned using a TAInstruments Q2000 DSC (Differential Scanning Calorimeter) with anauto-sampler, and a nitrogen purge rate of 50 ml/min. The heating ratewas 10° C./min and the temperature profile between 20° C., 200° C., andback to 20° C. was applied twice for each sample. The scans wereanalyzed using Universal Analysis V4.7A software. The glass transitiontemperature (Tg) onset temperature was determined as the inflectionpoint of the baseline step transition, reported in degrees Celsius.

REFERENCE EXAMPLE

This example illustrates some of the benefits of sodium carbonates andsodium borates as pH moderators as an additive in a flame retardantmasterbatch suitable for use in foams. Various amounts of theundesirable hydrogen bromide (HBr) are shown in Table 1, along with theamounts of sodium carbonate(Na₂CO₃), sodium bicarbonate(NaHCO₃), andtetrasodium pyrophosphate (TSPP) needed to moderate the HBr. As shown,TSPP is a less desireable moderator as significally more mass is neededto deal with the HBr than for sodium carbonate (Na₂CO₃) or sodiumbicarbonate (NaHCO₃).

TABLE 1 Amount of Amount Needed* HBr (ppm) (ppm) Na₂CO₃ NaHCO₃ TSPP 5033 53 83 100 66 105 166 200 133 210 333 *Assuming reaction is completedwithout hydrolysis

Further, as shown in Table 2, sodium carbonates and sodium borates aremuch more desirable moderators in that the byproducts of reaction withthe HBr present a lesser threat than reaction with TSPP. This can beseen by the pKa values shown below for each, illustrating the preferencefor sodium carbonate. Further, while both sodium tetraborate decahydratehave similar pka values, TSPP is not desirable because the counter acidsformed upon reaction of the sodium with bromide become successively moreaggressive as each sodium ion is removed from the molecule, resulting inundesirable pyrophosphoric acid. Sodium borates are more preferred, evenwith their lower solubility, because they form very mild acidic speciesin comparison.

TABLE 2 Solubility* Acid Dissociation Constant pH Moderator (g/L) pKa1pKa2 pKa3 Byproducts Sodium 217 6.0-8.0 <3.6 N/A* NaBR + CarbonateNaHCO₃ Sodium 20 9.2 12.7 13.8 NaBR + tetraborate Boric Acidsdecahydrate 67 9.3 6.7 2.1 Disodium Tetrasodium Pyrophosphate +pyrophosphate Pyrophosphoric Acid *in water (20° C., 68° F.)

Example 1

The following components were used to make a masterbatch composition.The base resin was a polystryrene resin in pellet form having a densityof 1.04 g/cm³ from PolyOne. The flame retardant was BLUEDGE™ polymericflame retardant FR63 in powder form having a density of 1.9 g/cm³ fromthe DuPont Co. The acid scavengers were cresol novolak epoxy resin CNE220 in pellet form from Chang Chun Chemical Corporation, and Plas-Chek775 Epoxidized Soybean Oil (ESO) in liquid form from Valtris SpecialtyChemicals. The antioxidant was Irgafos 168 in powder form from BASF, andthe soda ash from Univar in powder form.

A masterbatch composition was made in the following manner on a 25 mmtwin-screw extrusion system having one side feeder, as illustrated inFIG. 1. Specifically, the extruder had 9 barrels with a screw diameterof 25 mm and a length-to-diameter ratio of the screw, L/D=36/1. Theextruder temperatures were set to 180° C. and the die temperature wasset at 200° C.

A LiW brand loss-in-weight pellet feeder was used to feed pellets of lowmolecular weight polystyrene base resin to the main feed throat,followed by a second LiW brand loss-in-weight pellet feeder that fed amixture of the same low molecular weight polystyrene base resin pelletswith cresol novolak epoxy pellets. Preheated epoxidized soybean oil(ESO) was then fed and injected into the extruder by using two 1000DTeledyne ISCO syringe pumps. The flame retardant, soda ash, andantioxidant were pre-mixed and then fed into the side feeder, slowlyintroducing the powders to the extruder until the feed rate reached thetarget value. The compounded polymer melt then passed through a stranddie and was quenched in a water trough. The polymer strands were driedby an air blade and then pelletized by a pelletizer, which producedpellets of the masterbatch composition.

The total feed rate was 160 g/m in and the screw speed was maintained at170 rpm for all items; other processing conditions are summarized inTable 3. There was an ESO leakage issue for Items 5, 10 and 12 thatprevented the formation of good masterbatches for testing. Themasterbatch compositions that were made and the resultant data fromtesting those compositions are given in Table 4, including the importantproperties of TGA onset time, and Yellow index. The data illustratesthat the addition of the inexpensive soda ash allows the amount of themuch more expensive epoxy compounds to be reduced and still make amasterbatch having improved or equivalent properties.

TABLE 3 Temperature Die Pressure Item at Barrel #9 (° C.) (psi) 1 188182 2 192 266 3 191 352 4 190 283 5 — — 6 191 290 7 188 189 8 191 184 9190 381 10 — — 11 189 153 12 — — 13 193 490 14 195 179

TABLE 4 TGA Base Soda Irgafos onset Tg-2nd Resin CNE220 ESO FR63 Ash 168time Heating Yellow Item (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (min)(° 4 C.) Index 1 31.1 3.25 6.75 53.8 1 4.1 23.26 62.87 25.63 2 31.1 4.54.5 53.8 2 4.1 19.79 62.35 23.99 3 29.1 2 9 53.8 2 4.1 20.02 63.26 26.374 33.6 2 4.5 53.8 2 4.1 19.76 62.27 26.73 5 26.6 4.5 9 53.8 2 4.1 NA NANA 6 31.1 0 9 53.8 2 4.1 23.79 57.79 22.97 7 31.1 3.25 6.75 53.8 1 4.122.16 62.56 24.17 8 31.1 3.25 6.75 53.8 1 4.1 19.96 62.42 26.59 9 28.64.5 9 53.8 0 4.1 NA NA NA 10 33.1 4.5 4.5 53.8 0 4.1 22.21 68.09 26.5211 33.1 2 9 53.8 0 4.1 NA NA NA 12 35.6 2 4.5 53.8 0 4.1 22.7 65.45 28.413 34.5 4.5 4.5 53.8 0 2.7 20.8 66.2 28.33 14 31.1 3.25 6.75 53.8 1 4.122.53 58.83 25.79 NA—Not available

Example 2

Example 1 is repeated, however, one quarter of the amount of BLUEDGE™flame retardant is replaced with an equivalent amount by weightPYROGUARD SR 720 flame retardant. The results obtained are similar tothose in Table 4.

Example 3

Polystyrene copolymer was fed into an extruder at a temperature ofapproximately 200° C. and combined with a previously made masterbatch toform a molten polystyrene copolymer/masterbatch mixture to be made intofoams. The masterbatch was made as in Example 1 by combining apolystyrene resin base resin, a solid acid scavenger, a liquid acidscavenger, an antioxidant, and 1.5 weight percent soda ash, along withthe same amount of the BLUEDGE™ polymeric flame retardant FR63 powder(53.8 wt %). The amount of masterbatch used in the polystyrenecopolymer/masterbatch mixture was adequate to achieve a bromine loadingin the final foam of 0.35 weight percent. Very minor amounts ofadditives (e.g., talc, screw lubricant additive) were also added to theextruder to aid processing.

Extruded foams were then made from the molten polystyrenecopolymer/masterbatch mixture to confirm the composition was suitablefor making foams that would pass the fire retardancy and otherrequirements of the North American Building Code Standards for C578 andS701, including Underwriters Laboratory (UL) 723. To confirm theperformance of the foams, the molten polystyrene copolymer/masterbatchmixture was combined with various mixtures of blowing agents(hydrofluorocarbon, CO₂, and water) to form a series of foamablemixtures. Each foamable mixture was cooled and extruded through a slitdie into atmospheric pressure to form a series of foam boards. Theresulting foam boards had good skin quality, were free of blowholes, andhad foam densities ranging from 1.5 to 2.53 pounds per cubic foot. Thethicknesses of the foam boards varied between 1 and 2.12 inches as shownin Table 5. All of the foams further had a nominal bromine content of0.35 weight percent and had an L.O.I in excess of 24.

Table 6 further summarizes the foam properties relatable to the codesand standards, including Vertical Cell Size (VCS), Vertical CompressiveStrength (Vc), Extrusion Compressive Strength (Ec), HorizontalCompressive Strength (Hc), and Vc divided by the total of all three(Vc/Vc+Ec+Hc) which provides indication of balance of the cellorientation. The foams further had an open cell content of less than 5percent and a calculated thermal insulating performance of greater thanR5 per inch.

The resulting foams, therefore, fully met the fire retardancy and otherrequirements of the North American Building Code Standards for C578 andS701, including Underwriters Laboratory (UL) 723.

TABLE 5 Thickness Density Item (inches) (lb/ft³) 1 2.10 2.53 2 1.03 2.523 1.03 1.60 4 1.03 1.59 5 1.04 2.45 6 2.12 2.49 7 2.02 2.09

TABLE 6 VCS Vc Ec Hc Vc/ Item (mm) (psi) (psi) (psi) (Vc + Ec + Hc) 10.21 65.2 36.7 44.0 0.45 2 0.16 43.9 59.6 38.8 0.31 3 0.17 16.2 36.312.4 0.25 4 0.17 16.5 35.0 11.8 0.26 5 0.19 44.3 55.0 39.0 0.32 6 0.2566.0 36.1 41.4 0.46 7 0.17 45.2 32.9 27.7 0.43

What is claimed is:
 1. A masterbatch composition suitable for use as aflame retardant in extruded polymer foams, comprising: (a) 20 to 40parts by weight base resin comprising styrene homopolymer or copolymer;(b) 1 to 16 parts by weight acid scavenger comprising an epoxy-basedcompound; (c) 2 to 6 parts by weight antioxidant comprising an alkyl oraryl phosphite; and (d) 45 to 60 parts by weight flame retardantcomprising a non-hexabromocyclododecane (HBCD) brominated polymer orcopolymer; wherein the amounts of (a), (b), (c), and (d) total 100 partsby weight; the masterbatch composition further comprising (e) 0.6 to 10parts by weight of water soluble pH moderator, based on 100 parts ofbase resin plus the at least one water soluble pH moderator.
 2. Themasterbatch composition of claim 1 wherein the base resin contains 5 to10 parts by weight of water soluble pH moderator, based on 100 parts of(a) base resin plus (e) water soluble pH moderator.
 3. The masterbatchcomposition of claim 1 wherein the alkyl phosphite isbis(2,4-dicumylphenyl)pentaerythritol diphosphite,distearylpentaerythritol diphosphite, or di(2,4-di-(t-butyl)phenyl)pentaerythritol diphosphite.
 4. The masterbatch composition of claim 1wherein the aryl phosphite is tris(2,4-di-tert-butylphenyl)phosphite. 5.The masterbatch composition of claim 1 wherein the acid scavengercomprises a brominated epoxy compound.
 6. The masterbatch composition ofclaim 1 wherein acid scavenger comprises epoxy cresol novolac resin. 7.The masterbatch composition of claim 1 wherein acid scavenger comprisesepoxidized oil.
 8. The masterbatch composition of claim 7 wherein amajority by weight of the acid scavenger is epoxidized oil.
 9. Anextruded polymer foam comprising a masterbatch composition, themasterbatch composition comprising: (a) 20 to 40 parts by weight baseresin comprising styrene homopolymer or copolymer; (b) 1 to 16 parts byweight acid scavenger comprising an epoxy-based compound; (c) 2 to 6parts by weight antioxidant comprising an alkyl or aryl phosphite; and(d) 45 to 60 parts by weight flame retardant comprising anon-hexabromocyclododecane (HBCD) brominated polymer or copolymer;wherein the amounts of (a), (b), (c), and (d) total 100 parts by weight;the masterbatch composition further comprising (e) 0.6 to 10 parts byweight of a water soluble pH moderator, based on 100 parts of (a) baseresin plus (e) water soluble pH moderator.
 10. The extruded polymer foamof claim 9 wherein (e) contains 5 to 10 parts by weight of a watersoluble pH moderator, based on 100 parts of (a) base resin plus (e)water soluble pH moderator.
 11. The extruded polymer foam of claim 9wherein the alkyl phosphite is bis(2,4-dicumylphenyl)pentaerythritoldiphosphite, distearylpentaerythritol diphosphite, ordi(2,4-di-(t-butyl)phenyl) pentaerythritol diphosphite.
 12. The extrudedpolymer foam of claim 9 wherein the aryl phosphite istris(2,4-di-tert-butylphenyl)phosphite.
 13. The extruded polymer foam ofclaim 9 wherein the acid scavenger comprises a brominated epoxycompound.
 14. The extruded polymer foam of claim 9 wherein the acidscavenger comprises epoxy cresol novolac resin.
 15. The extruded polymerfoam of claim 9 wherein acid scavenger comprises epoxidized oil.
 16. Theextruded polymer foam of claim 15 wherein a majority by weight of theacid scavenger is epoxidized oil.
 17. A process for manufacturing amasterbatch composition suitable for use as a flame retardant inextruded polymer foams, comprising the steps of: a) providing a baseresin to a mixing device operating at temperature of 150 to 230° C. toform a molten base resin; b) contacting the molten base resin in themixing device with: i) acid scavenger comprising an epoxy-basedcompound; ii) antioxidant comprising an alkyl or aryl phosphite; iii)water soluble pH moderator; and iv) flame retardant comprising anon-hexabromocyclododecane (HBCD) polymer or copolymer  to form a moltenflame retardant masterbatch composition; and c) cooling the molten flameretardant masterbatch composition to form a solid flame retardantmasterbatch composition.
 18. The process for manufacturing a masterbatchcomposition of claim 17 further comprising the step of: d) pelletizingthe solid flame retardant masterbatch composition to form pellets. 19.The process for manufacturing a masterbatch composition of claim 17wherein in step b) the acid scavenger contacting the molten base resinis epoxidized oil, epoxy cresol novolac resin, or a brominated epoxycompound.
 20. The process for manufacturing a masterbatch composition ofclaim 19 wherein in step b) the molten base resin is contactedsequentially with both epoxidized oil and epoxy cresol novolac resin byseparate additions.
 21. The process for manufacturing a masterbatchcomposition of claim 17 wherein at least one of the acid scavenger, theantioxidant, or the water soluble pH moderator contacts the molten baseresin in the mixing device prior to the flame retardant contacting thebase resin.
 22. The process for manufacturing a masterbatch compositionof claim 21 wherein the acid scavenger contacts the molten base resin inthe mixing device prior to the flame retardant contacting the baseresin.